The Conclufion. 37 j 
perfpire much kfs than other trees, yet is 
the quantity they perfpire fo confiderable, 
that it has always been one of the greateft 
difficulties in the ordering of a Green-houfe 
to let in freffi air enough without expofmg 
the plants to too much cold. For fince the 
perfpiration of trees will not be free and 
kindly in a clofe damp air, the fap will be 
apt to ftagnate, which will make the plants 
grow moldy, or they will be fickly, by im- 
bibing fuch damp rancid vapours $ for by 
Mr. Miller's curious obfervations on the 
perfpiration of the ‘Plantain tree of the 
Weft-Indies, and of the Aloe under Experi- 
ment 5, plants will often imbibe moifture in 
the night as well in {loves as common Green- 
houfes without fire 5 it is certainly of as great 
importance to the life of the plants to dis- 
charge that infe&ed rancid air, by the ad- 
mittance of frefh, as it is to defend them from 
the extream cold of the outward air, which 
will deftroy them if let in immediately upon 
them. It feerns therefore to be a very reafon- 
able method which fomeufe, viz,, to cover 
fome of the inlets of their Greemhoufes on 
all fidcs with canvafs, and in extream cold 
weather withffiutters made of reed or ftraw, 
through which the air can only pafs in little 
ftreams : The like contrivance would pro- 
4 bably 
